Non-volatile memory (NVM) devices are able to retain stored data even when the power supply is interrupted. Non-volatile memory devices include flash devices which can be programmed using electrical signals. A NVM device, for example, includes a memory transistor and a select or access transistor in series. The memory transistor stores data programmed into the memory cell, while the access transistor selects the memory cell to be programmed or erased.
The memory transistor can be of various types. For example, the memory transistor may have a stacked gate structure having a control gate over a floating gate and a storage layer sandwiched between control and floating gates. In addition, an erase gate is disposed over a source. During fabrication of the memory devices, we have observed that unwanted dopants from implants are trapped the tunneling oxide separating the floating gate and erase gate. This causes damage to the tunnel oxide. In addition, bridging between the erase gate and control gate may cause shorting. These issues cause defects or failures, impacting device yields.
The present disclosure is directed to a memory cell with improved performance and reliability and the method of forming thereof.